1. Field of the Invention
The present invention describes a method of electrochemical synthesis of organic compounds using an electrochemical decarboxylation process (EDP), and more specifically such processes using custom electrolytes and ionic liquids. The EDP can be used to converts alkali salts of a variety of carboxylic acids to different hydrocarbon products. Carboxylic acids (RCO2H) make up a board class of organic compounds, where R can be an alkyl group, cycloalkyl group, an alkyenyl, and alkynyl group and an aryl group. The R group can also contain a hydrocarbon that may possess a heteroatom such as O, S, N, etc. The electrochemical decarboxylation disclosed in this patent removes CO2 from the carboxylic acid and creates a high energy radical or carbocation which can form carbon-carbon or carbon hydrogen bonds with other species present in solution. This process can be used to synthesize a variety of different types of organic compounds such as saturated hydrocarbons, diols, esters, olefins, aryl-alkyl compounds, etc. The electrochemical decarboxylation process is advantageous to other methods conventionally used to synthesize these compounds because it can be performed at moderate conditions and does not require the use of catalyst.
2. Description of the Related Art
Conventionally, electrochemical decarboxylation reactions are performed in polar organic solvents. Due to the versatility of the process there is not a single polar organic solvent that meets all the requirements needed for a universal electrolyte that can be applied to the decarboxylation of the vast amounts of carboxylic acids available. Other limitations of using common polar organic electrolytes are the limited carboxylic acid solubility and the electrolyte can be electrochemically oxidized during the decarboxylation process. The lack of a universal electrolyte limits the carboxylic acids that can be processed with the electrochemical decarboxylation process, and also limits the commercial application of such a process as the current efficiency and product selectivity is low because of the high number of side products that form from the oxidation of the solvent. Also, the use of polar organic solvents counter balances the environmental benefits afforded by the use of carboxylic acid precursors and the electrochemical decarboxylation process.
It would be advantageous to find an electrolyte system that has a high conductivity, is electrochemically stable, and can be modified for specific reactions to provide high solubility of the carboxylic acid precursors, low solubility of the hydrocarbon products, and minimizes the side reactions involving the electrolyte. It is one aim of the disclosed invention to prepare custom ionic liquids for use as electrolytes in the electrochemical decarboxylation, being designed for the specific decarboxylation process of interest. Ionic liquids are defined as liquids composed of ions that are fluid around or below 100° C., and exhibit low vapor pressure and can be reused with the appropriate design considerations. Ionic liquids are considered to be “designer” solvent systems, because the properties of the ionic liquids can be modified by changing the cation and anion of the liquid, and/or by modifying the structure of the cation and anion. Such an electrolyte system will improve the applicability and efficiency of the electrochemical decarboxylation process, distinguishing it as an alternative preparation method that is more economically and environmentally sustainable than the convention synthesis routes.